Radiation polymerizable acrylate-functional polysiloxanes have been described, for example, in U.S. Pat. No. 4,306,050 to Koennen, in which organopolysiloxanes having chlorine attached to silicon atoms are reacted with pentaerythritol triacrylate or pentaerythritol trimethacrylate. These compositions, however, require the use of highly irritating pentaerythritol acrylate derivatives and the acrylate group is linked to the silicon atom by a carbon-oxygen bond which is hydrolytically unstable.
U.S. Pat. No. 3,878,263 to Martin describes acrylate-functional polysiloxanes wherein the acrylate-functional group is bonded to the silicon atom via a hydrolytically stable carbon-silicon bond. However, these acrylate-functional polysiloxanes are generally slow to cure when irradiated with actinic radiation.
U.S. Pat. No. 4,201,808 to Cully describes acrylate-functional polysiloxanes wherein the degree of acrylation is increased by having acrylate groups linked to silicon atoms by silicon-carbon linkages as well as silicon-oxygen-carbon linkages; thereby enhancing the reactivity of the fluid when irradiated with actinic radiation.
U.S. Pat. No. 4,290,869 to Pigeon discloses a process for preparing photopolymerizable organopolysiloxanes by reacting hydroxy-terminated diorganopolysiloxanes with an acrylate-functional alkoxysilane in the presence of a titanate catalyst.
Generally, heat is required in preparing the acrylate-functional polysiloxanes to effect coupling of the acrylate-functional group to the siloxane or to effect removal of solvent and by-products. This has the disadvantage that the acrylate group is sensitive to heat and often induces polymerization of the acrylates.
Therefore, it is an object of this invention to provide novel acrylate-functional polysiloxanes. Another object of this invention is to provide novel acrylate-functional polysiloxanes that may be derived from polyacrylate oligomers that are less toxic than the pentaerythritol derivatives. Still another object of this invention is to provide acrylate-functional polysiloxanes in which some of the silicon atoms contain more than one acrylate group per molecule. A further object of this invention is to provide an acrylate-functional polysiloxane that is very reactive under radiation conditions even in the presence of oxygen. A still further object is to provide acrylate-functional polysiloxanes in which the acrylate containing group is bonded to the silicon atom via a silicon-carbon-nitrogen linkage. A still further object is to provide a process for making acrylate-functional polysiloxanes under conditions which do not induce polymerization of the acrylate groups. A still further object is to provide acrylate-functional polysiloxanes which are soluble in organic coating compositions.